qemu: command: Don't bother reporting errors in smbios formatters
qemu: command: Don't bother reporting errors in smbios formatters

qemuBuildSmbiosBiosStr and qemuBuildSmbiosSystemStr return NULL if
there's nothing to format on the commandline. Reporting errors from
buffer creation doesn't make sense since it would be ignored.

datto/libvirt,jfehlig/libvirt,VenkatDatta/libvirt,jardasgit/libvirt,eskultety/libvirt,VenkatDatta/libvirt,libvirt/libvirt,fabianfreyer/libvirt,taget/libvirt,eskultety/libvirt,taget/libvirt,andreabolognani/libvirt,nertpinx/libvirt,taget/libvirt,taget/libvirt,zippy2/libvirt,eskultety/libvirt,jardasgit/libvirt,nertpinx/libvirt,libvirt/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,olafhering/libvirt,andreabolognani/libvirt,nertpinx/libvirt,datto/libvirt,jfehlig/libvirt,olafhering/libvirt,datto/libvirt,VenkatDatta/libvirt,libvirt/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,nertpinx/libvirt,jfehlig/libvirt,jfehlig/libvirt,eskultety/libvirt,datto/libvirt,libvirt/libvirt,jardasgit/libvirt,crobinso/libvirt,datto/libvirt,nertpinx/libvirt,jardasgit/libvirt,zippy2/libvirt,fabianfreyer/libvirt,crobinso/libvirt,jardasgit/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,crobinso/libvirt,crobinso/libvirt,olafhering/libvirt,eskultety/libvirt,VenkatDatta/libvirt,taget/libvirt,zippy2/libvirt,olafhering/libvirt,zippy2/libvirt